The role of cell surface glycoproteins in mammary tumor metastasis will be examined. Two murine mammary adenocarcinoma sublines, TA3-Ha and TA3-St, will serve as the model system and will provide the glycoprotein fraction-1 (GPF-1) which has been suggested to interfere with the immunologic response of the host thereby enhancing metastasis (Sanford et al., 1973; Cooper et al., 1974). GPF-1 will be isolated and purified from viable cells and spent culture media by solubilization, perchloric acid extraction, gel filtration and affinity chromatography. The chemical composition and immunogenicity of GPF-1 in heterologous, syngeneic and allogeneic hosts will be determined. GPF-1 and its homologous antisera will be examined for cross-reactivity with H-2 alloantigens and oncornavirus antigens by immunodiffusion, immunofluorescence and immunoprecipitation. The role of GPF-1 in abrogating the immune response of the host against implanted mammary tumors will be ascertained by in vitro microcytotoxicity tests and in vivo challenge experiments. Other murine tumor cell cultures and lines will also be examined for the presence of GPF-1 like glycoproteins and their role in tumor metastasis in syngeneic and allogeneic systems. GPF-1 and GPF-1 like isolates will be compared for structural and antigenic similarities, and their ability to enhance growth of heterologous murine mammary tumors.